The invention relates to polymers used in chemically amplified resist compositions, and resist compositions including such polymers.
With increasing integration of semiconductor devices, there may be a heightened need to form finer patterns of subquarter micron capacity in photolithography processes. A photolithography technology has been proposed which may use an ArF eximer laser (193 nm) for devices beyond the 1 giga capacity. This technology may be intended to replace conventional KrF eximer lasers using deep ultraviolet rays (e.g., 248 nm). Accordingly, it may be desirable to develop new chemically amplified resist compositions.
In general, the prerequisites for chemically amplified resist compositions for use with an ArF eximer laser may be as follows: (1) transparency in the range of 1 93 nm; (2) excellent thermal characteristics, such as for example, high glass transition temperature (Tg); (3) excellent adhesion to film materials; (4) excellent resistance against a dry etching process; and (5) capability of being developed using a conventional developer. An example of one polymer which has been developed to possibly possess the above properties is a tetrapolymer, namely poly (IBMA-MMA-tBMA-MAA) which is represented by the general formula: 
The above tetrapolymer may not be satisfactory. In particular, the tetrapolymer may have a very weak resistance against an etching process and may have weak adhesive properties. Additionally, a special developer may be needed for the development of the tetrapolymer. To potentially address the above problems, a class of cyclopolymers have been proposed which are of the general formula: 
These cyclopolymers, however, also potentially suffer from drawbacks. Specifically, the cyclopolymers may have weak adhesive properties, and as a result lifting may possibly occur at the resist. Moreover, a special developer which may require separate preparation and may have to be employed in a specific concentration range might have to be used with the above cyclopolymers in place of generally accepted developers.
In view of the above, it is an object of the present invention to provide polymers for use in chemically amplified resists which may be exposed to light using ArF lasers, may have strong resistances to dry etching processes, may possess excellent adhesion to film materials, and may be developed using conventional developers.
It is also an object of the present invention to provide chemically amplified resists containing such polymers.
These and other objects, features, and advantages of the present invention are provided by polymers for use in chemically amplified resists. In one aspect, the invention relates to copolymers for use in chemically amplified resists. The copolymers are of the general formula (1): 
In the above formula (I), R1 is selected from the group consisting of hydrogen and C1 to C10 aliphatic hydrocarbons, with the aliphatic hydrocarbons containing substituents selected from the group consisting of hydrogen, hydroxy, carboxylic acid, carboxylic anhydride, and combinations thereof. R2 is selected from the group consisting of hydrogen and C1 to C10 aliphatic hydrocarbons, with the aliphatic hydrocarbons containing substituents selected from the group consisting of hydrogen, hydroxy, carboxylic acid, carboxylic anhydride, and combinations thereof; and n represents integers. The copolymers have weight average molecular weights ranging from about 3,000 to about 100,000.
In another aspect, the invention provides terpolymers for use in chemically amplified resists. The terpolymers are represented by the general formula (II): 
In the above formula (II), R3 is selected from the group consisting of hydrogen and C1 to C10 aliphatic hydrocarbons, with the aliphatic hydrocarbons containing substituents selected from the group consisting of hydrogen, hydroxy, carboxylic acid, carboxylic anhydride, and combinations thereof. R4 is selected from the group consisting of hydrogen and C1 to C10 aliphatic hydrocarbons, with the aliphatic hydrocarbons containing substituents selected from the group consisting of hydrogen, hydroxy, carboxylic acid, carboxylic anhydride, and combinations thereof. R5 is selected from the group consisting of hydrogen and methyl. R6 is selected from the group consisting of t-butyl and tetrahydropyranyl, and m and n each represent integers. The ratios n/(m+n) range from about 0.1 to about 0.5.
In yet another aspect, the invention provides resist compositions which may include the copolymers and terpolymers described above.